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Inverted landscape of a Plio-Pleistocene phreatomagmatic monogenetic volcanic field in the Bakony-Balaton Upland

Hungary

Basaltic mesas in the Tapolca Basin representing preserved proximal part of former maar-diatreme volcanoes. Lake Balaton is in the background. Photo by: Norbert Mészáros.

Basaltic mesas in the Tapolca Basin representing preserved proximal part of former maar-diatreme volcanoes. Lake Balaton is in the background. Photo by: Norbert Mészáros.

Geological Period

Pliocene to Pleistocene

Main geological interest

Geomorphology and active geological processes
Volcanology

Location

Bakony–Balaton Region, Western Hungary, Hungary
46°50’38”N, 017°27’07”E

Basaltic mesas in the Tapolca Basin representing preserved proximal part of former maar-diatreme volcanoes. Lake Balaton is in the background. Photo by: Norbert Mészáros.

One of the best examples on Earth of completely inverted relief of a high vent-density phreatomagmatic monogenetic volcanic field.

Inverted landscapes are common features on Earth, but those composed of closely spaced phreatomagmatic volcanoes once filled with lava are rare. The Tapolca Basin has a visually attractive and geologically unique landscape produced by advanced geomorphic inversions on Earth (Wijbrans et al., 2007; Kereszturi and Németh, 2012). Following volcanism, ideal climatic conditions for erosion to act and a unique geological setting that is dominated by the presence of hard basement rocks covered by erodible fluvio-lacustrine successions led to a dramatic inverted landscape.

Columnar jointed basalt of the former lava lake within the Zalahaláp maar-diatreme craters demonstrates complex cooling history of lava. Photo by: Barnabás Korbély.

Columnar jointed basalt of the former lava lake within the Zalahaláp maar-diatreme craters demonstrates complex cooling history of lava. Photo by: Barnabás Korbély.

  • Geological description

Tapolca Basin is the core of the Mio-Pleistocene Bakony–Balaton Uplands monogenetic volcanic field. In this area volcanic erosion remnants are closely spaced, and significant erosion produced a globally unique, aesthetically attractive inverted landscape (Németh and Martin, 1999). The preserved volcanic successions provide ample evidences that the volcanism was driven primarily by explosive magma and external water interaction to form volcanic landforms such as maar and tuff ring volcanoes (Martin and Németh, 2007; Kereszturi et al., 2011). These volcanoes have broad and deep craters that operated as sediment traps or more frequently hosted scoria cones, lava flows and in some cases lava lakes locked within the crater walls. The differential erosion relatively quickly removed the tephra rings around the wide craters and carved into the pre-volcanic fluvio-lacustrine sand, silt and mud layers leaving behind basalt lava and agglutinated scoria successions as hill tops. The volcanoes of the Tapolca Basin represent a volcanic flare-up between 4.5 and 3 millions of years ago. Erosion made typical volcanic buttes marking a geomorphological level similar to the paleosurface these volcanoes erupted on. World-class examples of columnar jointed basalt, peperite and diatreme-filling pyroclastic rocks complete the geological wonders of this region.

  • Scientific research and tradition

Over 150 years of research made this region a type locality of landscape evolution studies and provided for internationally significant research (Martin and Németh, 2004). Basalt petrogenesis, monogenetic volcanism and volcanic geology aspects of maar-diatreme volcanism among the core subjects made this region an iconic locality of monogenetic volcanism research.

1 to 100,000 scale geological map [https://map.mbfsz.gov.hu/fdt100/] of the vicinity of the Tapolca Basin on SRTM30 shaded relief map. Quaternary - grey/beige; Neogene volcanics – green; Pliocene fluvio-lacustrine deposits – yellow; Mesozoic - blue/purple; Paleozoic - brown.

1 to 100,000 scale geological map [https://map.mbfsz.gov.hu/fdt100/] of the vicinity of the Tapolca Basin on SRTM30 shaded relief map. Quaternary – grey/beige; Neogene volcanics – green; Pliocene fluvio-lacustrine deposits – yellow; Mesozoic – blue/purple; Paleozoic – brown.

  • Reference

Kereszturi, G. et al. (2011) ‘The role of external environmental factors in changing eruption styles of monogenetic volcanoes in a Mio/Pleistocene continental volcanic field in western Hungary’, Journal of Volcanology and Geothermal Research, 201(1), pp. 227–240. Available at: https://doi.org/10.1016/j.jvolgeores.2010.08.018.

Kereszturi, G. and Németh, K. (2012) ‘Structural and morphometric irregularities of eroded Pliocene scoria cones at the Bakony–Balaton Highland Volcanic Field, Hungary’, Geomorphology, 136(1), pp. 45–58. Available at: https://doi.org/10.1016/j.geomorph.2011.08.005.

Martin, U. and Németh, K. (2004) Mio/Pliocene phreatomagmatic volcanism in the western Pannonian Basin. International Maar Conference, Budapest: Geological Institute of Hungary (Geologica Hungarica. Series geologica, t. 26).

Martin, U. and Németh, K. (2007) ‘Blocky versus fluidal peperite textures developed in volcanic conduits, vents and crater lakes of phreatomagmatic volcanoes in Mio/Pliocene volcanic fields of Western Hungary’, Journal of Volcanology and Geothermal Research, 159(1), pp. 164–178. Available at: https://doi.org/10.1016/j.jvolgeores.2006.06.010.

Németh, K. and Martin, U. (1999) ‘Late Miocene paleo-geomorphology of the Bakony-Balaton Highland Volcanic Field (Hungary) using physical volcanology data’, Zeitschrift für Geomorphologie, 43(4), pp. 417–438. Available at: https://doi.org/10.1127/zfg/43/1999/417.

Wijbrans, J. et al. (2007) ‘40Ar/39Ar geochronology of Neogene phreatomagmatic volcanism in the western Pannonian Basin, Hungary’, Journal of Volcanology and Geothermal Research, 164(4), pp. 193–204. Available at: https://doi.org/10.1016/j.jvolgeores.2007.05.009.

  • Author(s)

Barnabás Korbély.
Bakony–Balaton Geopark Group, Balaton Uplands National Park Directorate, Csopak, Hungary.

Károly Németh.
Saudi Geological Survey, Kingdom of Saudi Arabia.

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